1. Field of the Invention
The present invention relates generally to novel 5-iodo-6-amino-1,2-benzopyrones and their metabolites, very potent, selective and safe cytostatic and antiviral agents, and to a method of treatment of tumorigenic and viral diseases using 5-iodo-6-amino-1,2-benzopyrones and their metabolites. More specifically, it relates to the use of 5-iodo-6-amino-1,2-benzopyrones, their homologues and salts, in suppressing and inhibiting the tumorous and metastatic growth and the growth of certain viruses in a mammalian host.
2. The State of Art and Related Disclosures
Both tumorigenic growth and viral infections become a most serious threat to modern society. Malignant cancerous growths became, due to their unique characteristics, one of the most serious diseases encountered by modern medicine. These characteristics are: uncontrollable cell proliferation which results in unregulated growth of malignant tissue, lack of differentiation and ability to invade local and even remote tissues, lack of detectable symptoms and the last but not the least, the lack of effective therapy and prevention.
Cancer can develop in any tissue of any organ at any age. The etiology of cancer is not clearly defined but mechanisms such as genetic susceptibility, chromosome breakage disorders, viruses, environmental factors and immunologic disorders have all been linked to a malignant cell growth and transformation.
The above is particularly true in view of extreme secondary side effects found to be accompanying all currently available forms of cancer therapy. The success of surgery, the most radical treatment, depends on the stage when the cancer growth is discovered. If the whole tumor is discovered and removed before the metastases develop, then the surgery is effective. In the majority of cases, however, the cancer is discovered too late for surgery to be effective as the only treatment. Two other available therapies, such as radiotherapy, or chemotherapy are accompanied by severe adverse reactions. For radiation, sublethal doses are often required which directly affect the cell content and function.
Antineoplastic chemotherapy currently encompasses several groups of drugs. Alkylating agents alkylate cell proteins and nucleic acids thus preventing cell replication, disrupt the cell metabolism and lead to a cell death. Typical alkylating agents are nitrogen mustard, cyclophosphamide and chlorambucil. Toxicities associated with alkylating agents treatment include nausea, vomiting, alopecia, hemorrhagic cystitis, pulmonary fibrosis and an increased risk of development of acute leukemia. Purine, pyrimidine and folate antogonists are cell cycle and phase specific and, in order to promote anti-tumor effect, they require cells to be in the cell replication cycle and in the DNA synthesis phase of replication. The purine antagonists such as 6-mercaptopurine or 6-thioguanidine inhibit de novo purine synthesis and interconversion of purines. The pyrimide antagonists, such as cytarabine, 5-fluorouracil or floxuridine inhibit DNA synthesis by inhibiting deoxycytidylate kinase and DNA polymerase. Folate antagonists, methotrexates bind tightly with the intracellular enzyme dihydrofolate reductase, ultimately causing cell death from inability to synthesize pyrimidines. Toxicities associated with the use of these compounds include alopecia, myelosuppression, vomiting, nausea, and cerebellar ataxia, among others.
Plant alkaloids such as vincristine, vinblastine or podophyllotoxins etoposide and teniposide generally inhibit mitosis and DNA synthesis and RNA dependent protein synthesis. Toxicities of these drugs are similar to those described above and include myopathy, myelosuppression, peripheral neuropathy, vomiting, nausea and alopecia.
Antitumor antibiotics such as doxorubicin, daunorubicin and dactinomycin act as intercalators of DNA, preventing cell replication, inhibiting synthesis of DNA-dependent RNA and inhibiting DNA polymerase. Bleomycin causes scission of DNA and mitomycin acts as inhibitor of DNA synthesis by bifunctional alkylation. Toxicities of these antibiotics are numerous and severe and include necrosis, myelosuppression, anaphylactic reactions, anorexia, dose-dependent cardiotoxicity and pulmonary fibrosis.
Other compounds used for chemotherapeutical treatment of cancer are inorganic ions such as cisplatin, biologic response modifiers such as interferon, enzymes and hormones. All these compounds, similarly to those mentioned above, are accompanied by toxic adverse reactions and consequently their use, as those others, is either limited or causes severe side effects.
Thus, it would be extremely advantageous to provide chemotherapeutic treatment which would effectively inhibit cancer cell proliferation and suppress neoplastic growth and would, at the same time be safe and non-toxic (The Merck Manual, 1218-1225 (1987), 15th Ed.). Novel compounds of this invention provide such treatment.
Similarly, the high degree of infectiousness and a fast reproduction cycle of viruses within the host organism, combined with essentially no effective treatment available aside from largely toxic deoxyribonucleotide homologs, make the viruses a nuisance and health hazard which the human population encounters on daily basis.
Viruses generally are very resistant to any treatment and some of them, for example herpes simplex viruses or cytomegalovirus, once inside the body, may remain forever in a dormant state until the resistance is weakened. The others, such as human immunodeficiency viruses are nearly always fatal.
There is no simple treatment of viral diseases. They are not susceptible to antibiotics and there is no other available treatment of viral diseases other than by chemotherapy which inhibits viral replication in the host cells (The Merck Manual, 170 (1982), 14th Ed.). Examples of these chemical agents are idoxuridine useful for treatment of herpes simplex keratitis and known viral replication inhibitors acyclovir, ribavirin, vidarabine, gancyclovir, adenine arabinoside (ARA-A) and AZT. These, and other viral replication inhibitors, however, are known to be cytotoxic, hepatotoxic, neurotoxic, nephrotoxic and were shown to have teratogenic effects (Virus Diseases, 1-6 (1978), Crown Publishers, N.Y.).
Thus it would be highly desirable to have available an effective and yet nontoxic treatment of viral diseases.
Human immunodeficiency virus (HIV) infections known as acquired immunodeficiency syndrome (AIDS), presently constitute one of, if not the most, pressing health hazards worldwide. HIV infections are almost always fatal due to a weakened immunoresistance, and due to accompanying opportunistic infections, malignancies and neurologic lesions leading to an early death.
There is no effective treatment for AIDS other than the treatment of the opportunistic infections, neoplasms and other complications. Available cytostatic (AZT) and antiviral (acyclovir) drugs are extremely toxic and cause severe adverse reactions. The most promising of all currently investigated drugs seem to be antivirals which may somehow inhibit the viral reproduction enzyme, reverse transcriptase (The Merck Manual, 288 (1987) 15th Ed..
To provide an effective and yet non-toxic antiviral drug which would affect the reproduction of HIV would thus be of extreme importance and a life saving measure for many thousands of AIDS victims.
Herpes simplex virus type-1 and 2 similarly are wide spread infections. They may occur in AIDS patients as one of the opportunistic infections. Type-1 HSV strain (HSV-1) commonly causes herpes labialis located on a lip, and keratitis, an inflammation of the cornea. Type-2 HSV is usually located on or around the genital area and is generally transmitted primarily by direct contact with herpetic sore or lesions. HSV-2 has been related to the development of uterine cancer.
Herpes simplex virus is very infectious and is rapidly and easily transferable by contact. There is no specific therapy to this extremely painful viral infection. Current treatment of HSV infections is primarily by systemic administration of above mentioned antiviral drugs which treatment is accompanied by undesirable adverse reactions as those described previously.
The antiviral agents used for HSV treatment are not selective inhibitors of HSV replication but affect also the replication of normal cells. Therefore, when used in doses large enough to seek and destroy all the active herpes viruses dormant in the sensory ganglia, these compounds may also be highly disruptive to the normal DNA in the host cells in which the virus multiplies. This is a very undesirable effect since the replication of normal cells is also affected.
Thus, it would be advantageous to have available non-toxic treatment of HSV infections.
Cytomegalovirus (CMV), a dangerous co-infection of HIV, is a subgroup of highly infectious viruses having the propensity for remaining latent in man. CMVs are very common among the adult population and as many as 90% of adults have been exposed to and experienced CMV infections. CMVs are normally present in body fluids such as blood, lymph, saliva, urine, feces, milk, etc. CMV infections may cause spontaneous abortion, stillbirth, postnatal death from hemorrhage, anemia, severe hepatic or CNS damage. Particularly dangerous are CMV infections afflicting AIDS patients, where CMV may cause pulmonary, gastrointestinal or renal complications. There is no specific therapy for CMVs. Contrary to the HSV, CMV is resistant to acyclovir, and to other known antiviral drugs.
Thus, it would be extremely advantageous to have available a drug which would effectively inhibit CMV infections.
The existing chemotherapeutical treatment of the most neoplastic growth and of viral infections is thus mostly limited to very toxic agents and antivirals.
Cellular and molecular events leading to malignant transformation and potential viral involvement in it are poorly understood. However, genotypically, a given cancer is believed to arise from a clone of transformed cells.
Retroviruses contain an enzyme called reverse transcriptase that can convert viral RNA in the cytoplasm into DNA, which may replicate from extrachromosomal sites or move into the cell nucleus where it becomes part of the host cell DNA. These integrated viral genes are duplicated with normal cellular genes, and all progeny of the originally infected cells will contain the viral genes. Expression of the viral genes for some retroviruses may be oncogenic, converting the cell into a cancer, or may have other pathologic effects which may alter normal cell function or produce cell death.
It is therefore a primary object of this invention to provide non-toxic, highly effective antineoplastic and antiviral drugs. 5-iodo-6-amino-1,2-benzopyrones (5-I-6-ABP) and their analogs demonstrate these desired properties.
These drugs have been now found to be agents of remarkably low toxicity, yet highly effective inhibitors of tumorigenic and viral replication in cell cultures and in human blood. Their therapeutic spectrum appears to be particularly useful for suppression and inhibition of cancer growth and for treatment of the most dangerous viral infections, such as AIDS and herpetic infections.
5-iodo-6-aminobenzopyrones have not been hitherto known or described. The only remotely related compounds found in the literature are 6-amino-benzopyrone (6-ABP) described in J. Pharmo Soc. Jap., 498:615 (1923) and 3-amino-6-iodo-8-methoxy-1,2-benzopyrone, described in J. Ind. Chem. Soc., 48:375 (1971). However, only scarce medicinal use for the first substance has been reported, although the testing was done for its sedative and hypnotic effects (J. Pharm. Soc. Japan, 73:351 (1953) and Ibid, 74:271 (1954), hypothermal action Yakugaku Zasshi, 78:491 (1958), and antipyretic, hypnotic, hypotensive and adrenolytic action was reported, Ibid, 83:1124 (1963). No significant action for any of those uses was found. No medical use was reported for the second compound.
The precursor molecule, 1,2-benzopyrone (coumarin), was shown to be an inhibitory ligand of adenosinediphosphoribose transferase (ADPRT), a DNA-binding nuclear protein present in neoplastic cells (Proc. Nat. Acad. Sci. (USA), 84:1107 (1987)).
Recently, 6-ABP was shown to specifically bind to ADPRT at the same site that also binds catalytically effective DNA termini. It is evident that both 6-ADP and DNA compete for the same site on ADPRT. These results were disclosed in FEBS Lett., 212:73 (1987), where the biological role of ADPRT was studied extensively with the aid of synthetic ligands of ADPRT and shown to inhibit DNA proliferation, particularly in tumorigenic cells. Potential antiviral effects of these ligands on viral replication was now studied and found and is the subject of the copending invention entitled "6-Amino-1-2-Benzopyrones useful for Treatment of Viral Diseases," Ser. No. 585,231, filed on Sep. 21, 1990 which is hereby incorporated by reference.
The primary objective of this invention is the discovery that novel 5-iodo-6-aminobenzopyrones (5-I-6-ABP), are specific, selective, potent and non-toxic antitumorigenic and antiviral agents. The testing of these compounds on various cancer cells and virally infected cultures, including HIV, showed that 5-I-6-ABPs are particularly useful for inhibition and suppression of cancer cell growth, and on HIV, HSV and CMV replication.